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  Topic: Lou FCD's photo corner, Technics, equipment, photos...< Next Oldest | Next Newest >  
Wesley R. Elsberry



Posts: 4502
Joined: May 2002

(Permalink) Posted: April 21 2012,14:08   

Quote (midwifetoad @ April 21 2012,07:11)
Well we could always convert this into an argument about gnu atheism, but seriously, my comment had a very limited scope. I had no idea I was disagreeing with anything you said.

If you are reviewing lenses on the basis of transmission, you would be lenses of the same type, as in different brands and models.

Incident light metering is rather specialized. It's used in studios and in movie making, but I think anyone going to that kind of trouble would calibrate a system with actual test shots.

Back when shutters were mechanical and involved a moving slit of varying width, it was widely recognized that effective shutter speed didn't necessarily match nominal speed.

And if you developed your own film you noticed differences between brands and types of developer. I read, for example, that National Geographic had all of their film processed in one plant, and did not allow it to be done as the first batch of the day. They wanted assurance that the chemistry was right.

For 99.9 percent of people using digital cameras, these issues are irrelevant, even if interesting. I would bet not many people shooting RAW images would notice half an f-stop difference in exposure. In fact people routinely adjust the levels in their photos to make them "pop."

This can easily truncate several f-stops of shadow and highlight detail.

I think I'm getting to where I understand how my experience of your comment differed so completely from how you perceived your comment. At least part of the utility of the concept of f-stops is universality, a metric that applies to all lenses and light-passing gizmos. It allows comparison. Your comment, though, with the "irrelevant" phrasing looked to me that it simply assumed that comparison itself was not an issue of interest, and only use of a specific lens with a specific camera feature mattered.

That other parts of a photographic system have slop in them is not a reason to bypass understanding of one particular part. Nor do I find polling useful in determining whether to pay attention to and learn a technical topic. Most people don't have a clue about genetics and no demographically broad practical need to know more; should we discourage learning about the technical details as "irrelevant" there?

Let's look at what you say about comparison here:

 
Quote

If you are reviewing lenses on the basis of transmission, you would be lenses of the same type, as in different brands and models.


This is, again, much too glib.

One can easily have a comparison among multiple lenses in the same brand. Nikon makes and has made quite a variety of 85mm short telephoto lenses. The second link from my last message shows an example of a run of Nikkor 85mm lenses whose multi-coating is particularly ineffective. If one buys lenses used, knowing about this difference could result in one buying a better, higher-transmission lens from later in production. That would be a case of same brand, same model, and same marked f-stop. Or choosing which particular 85mm model to buy could involve a tradeoff between the actual light-transmitting characteristics and one's pocket-book. This isn't a simple function of adding a constant to the f-stop of all the choices.

Nor does the restriction of "same type" necessarily hold. One might choose between a zoom lens and a prime lens for a job based on light transmission. Whether one makes that decision might well be influenced by whether the circumstances permit the difference in T-stops between the two rather than f-stops. For concert photography, an additional T-stop difference as opposed to the marked f-stop difference might well tip the balance in favor of the prime lens, where the marked f-stop difference might have been an acceptable tradeoff for the convenience of the zoom, but the T-stop difference would not be.

Of course, f-stop versus T-stop is just one of many factors that would go into a lens purchase or use decision, but given the hard constraints of available light photography, it is one that will continue to engage -- and reward -- photographers looking for the very best results.

Automatic systems help produce passable results for lots of people. The Kodak Brownie camera was a huge hit in the late 1800s because it allowed people to use photography without all that difficult mucking about with picking exposure times and such-like. The fact that Brownie technology existed did not obviate the knowledge garnered by people who chose to keep on with their view cameras and glass plates. Nor do the very much improved automatic systems of today render knowledge of systems under physical constraints "irrelevant". If you only have one lens (or one lens per activity) and you simply rely on automation, conceptually it doesn't make much difference whether the camera you use is called a "Canon 5D MkII", "Nikon D700", "Holga", or "Kodak Brownie".

It's a difference between knowing your tools and "Whatever". A lot of people can (and do) get by with "Whatever", but anyone who has come away with a blurry mess where they had visualized a sharp decisive moment may well want to reconsider adherence to "Whatever" as a photographic learning strategy.

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"You can't teach an old dogma new tricks." - Dorothy Parker

    
  43 replies since April 18 2012,05:59 < Next Oldest | Next Newest >  

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